There is no point putting anything on top of a crusty surface, but if you spend the time cleaning the rust off and apply Lanoguard as per instructions it will preserve the underside for many years to come
This is before and after cleaning of my old Volvo two years ago. There was no rust just 23 years of dirt accumulation. Cleaned with soapy water, turpentine, brushes, plenty cloths then when clean apply Chemical Guys Bare Bones to finish it off
This is after Lanoguard was applied this year (2 years after cleaning)
